Flame-sensing bulb construction

ABSTRACT

A condition sensing bulb portion interconnected to capillary tube means that provides fluid communication therethrough to the chamber of the bulb portion whereby the tube and the bulb portion define a juncture area therebetween. Insulating means is carried by the device for insulating the juncture area at the exterior thereof so that substantially no adverse wide temperature gradient can be created between the bulb portion and the juncture area when the bulb portion is subjected to relatively high temperatures provided by flames imposed on the bulb portion. Such insulating means can be a metal sleeve disposed about the juncture area to provide a dead airspace about the juncture area.

United States Patent Genbauffe [54] FLAME-SENSING BULB CONSTRUCTION 72Inventor: Francis s. Genbaulte, Irwin, Pa.

[73] Assignee: Robertshaw Controls Richmond, Va.

[22] Filed: Jan. 19,1970

[21] Appl.No.: 3,818

[56] References Cited UNITED STATES PATENTS 1,850,646 3/1932 RossWatt..73/368 X 1 Feb. 15,1972

Porland ....236/99 3,400,886 9/ 1968 Holtkamp 236/ 1 5 [57] ABSTRACT Acondition sensing bulb portion interconnected to capillary tube meansthat provides fluid communication therethrough to the chamber of thebulb portion whereby the tube and the bulb portion define a juncturearea therebetween. Insulating means is carried by the device forinsulating the juncture area at the exterior thereof so thatsubstantially no adverse wide temperature gradient can be createdbetween the bulb portion and the juncture area when the bulb portion issubjected to relatively high temperatures provided by flames imposed onthe bulb portion. Such insulating means can be a metal sleeve disposedabout the juncture area to provide a dead airspace about the juncturearea.

8 Claims, 2 Drawing Figures FLAME-SENSING BULB CONSTRUCTION Thisinvention relates to a condition responsive device as well as to amethod for making such a condition responsive device or the like.

It is well known that condition responsive devices have been provided inthe past which are responsive to the existence of a flame at a burnermeans, such devices each having a flamesensing bulb portion disposed inthe flame area and containing expansible and contractable means, such asa fluid, which is expanded in the bulb portion when flames exist at theburner, the expanding means being transmitted by a capillary tube or thelike to a power element which has an expansible and contractable wallportion that operates valve means, electrical switches, etc.

It has been found according to the teachings of this invention that ifin the case of such prior known condition responsive devices a widetemperature gradient is created between the bulb portion and thejuncture area defined where the bulb portion is interconnected to thetube means interconnected thereto when the bulb portion is subjected torelatively high temperatures provided by the flames being imposeddirectly thereon, the juncture area readily deteriorates and fails andthereby provide a relatively short life for the condition responsivedevice.

Accordingly, it is a feature of this invention to provide means forpreventing such adverse wide temperature gradient between the bulbportion and the juncture area.

In particular, one embodiment of this invention provides a cylindricalmetal sleeve that has a first portion telescopically disposed about thebulb portion and a second portion extending from the bulb portion intelescoping spaced relation about the juncture area between the bulbportion and the tube means and along the tube means for a predetermineddistance to provide a substantially dead airspace completely about thejuncture area so as to prevent an adverse wide temperature gradientbeing created between the bulb portion and the juncture area so that thejuncture area remains at substantially the same temperature as the bulbportion whether or not the bulb portion is being immersed in flames.

Accordingly, it is an object of this invention to provide an improvedcondition responsive device having one or more of the novel features setforth above or hereinafter shown or described.

Another object of this invention is to provide an improved method ofmaking such a condition responsive device or the like, the method ofthis invention having one or more of the novel features set forth aboveor hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of this description which proceeds with reference to theaccompanying drawings forming a part thereof and wherein:

FIG. 1 is a fragmentary side view, partially in cross section,illustrating a prior art flame-sensing means.

FIG. 2 is a view similar to FIG. 1 and illustrates the improvedflame-sensing means of this invention.

While the various features of this invention are hereinafter describedand illustrated as being particularly adapted to provide flame-sensingmeans for a pilot burner means or the like, it is to be understood thatthe various features of this invention can be utilized singly or in anycombination thereof to provide condition responsive means for otherarrangements as desired.

Therefore, this invention is not to be limited to only the embodimentillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to FIG. 1, a prior art condition responsive device isgenerally indicated by the reference numeral and comprises a bracketmeans 11 carrying a pilot burner means 12 having an outlet means 13 forthe issuing of fuel that is ignited in a conventional manner to produceflames 14 that are directed by a flame shield 15 of the pilot burner 12about a flame-sensing bulb portion 16 having one end 17 thereof receivedin an opening means 18 of the flame shield 15 and the other end 19thereof interconnected to a capillary tube 20 in a conventional mannerthat defines a juncture area 21 therebetween. A relatively thickcylindrical sleeve 22 is telescoped about the tube 20 so as to carry thesame and has one end 23 thereof abutting against the juncture area 21between the tube 20 and bulb 16 whereby the sleeve 22 can be received insuitable opening means 24 in the bracket means 11 to support the otherend 19 of the bulb 16 in a generally horizontal position so that thebulb 16 will be fully immersed in the flames 14 when such flames 14 arecreated at the outlet 13 of the pilot burner means 12.

The bracket means 11 also is utilized to mount the pilot burner means 12and bulb arrangement 16 in a suitable position in the apparatus ordevice receiving the same.

It has been found that during the operation of the condition responsivedevice 10 of FIG. 1 over a relatively short period of time, such asthree months, the condition responsive device 10 failed in the juncturearea 21 between the bulb portion 16 and the tube means 20.

Accordingly, this invention solves such failure problem at the juncture21 between the tube means 20 and bulb portion 16 of the device 10 ofFIG. 1 as well as for similar devices.

In particular, it was found, according to the teachings of thisinvention, that a high temperature gradient was being created betweenthe bulb portion 16 and the juncture area 21 between the bulb 16 andtube 20 because the flame 14 of the burner 12 surrounded the bulbportion 16 while the bracket means 1 l at the opening means 24 thereofbeing disposed in intimate contact with the sleeve 22 and thecylindrical sleeve 22 being disposed in intimate contact with the tube20 acted as a heat sink or a highly conductive path for directing theheat of the juncture area 21 therefrom so that the juncture area 21 wasat a relatively low temperature while the bulb portion 16 was at arelatively high temperature. The wide temperature gradient is believedto be the cause of the failure problem in the juncture area 21 of thedevice 10.

Therefore, one of the features of this invention is to provideinsulation means about the juncture area 21 so as to prevent an adversetemperature drop in the juncture area 21 when the bulb 16 is beingheated by'the flames 14 whereby no adverse wide temperature gradient canbe created between the bulb portion 16 and the juncture area 21.

Accordingly, reference is now made to FIG. 2 wherein the conditionresponsive means of this invention is generally indicated by thereference numeral 30 and comprises the bracket means 11A, pilot burnermeans 12A and flame shield 15A of the prior art device 10. However, thebulb portion 31 of the condition responsive means 30 of this invention,while being shaped slightly differently at the free end 32 thereof thanat the free end of the bulb 16 of FIG. 1, could be of the sameconfiguration as the bulb portion 16 if desired. The bulb 31 isinterconnected by a juncture area 33 -to the capillary tube 34 thatleads to the control device 35 which, in the embodiment of FIG. 2,comprises an electrical switch means 36 operated by themovable wallmeans 37 of expandible and contractable power element 38 in a mannerconventional in the art. While the bulb portion 31 and tube 34 areintegral so that the juncture area 33 is integral therewith as will beap-.

parent hereinafter, it is to be understood that the tube 34 and bulb 31could be separate parts subsequently secured together to define thejuncture area 33.

In order to insulate the juncture area 33 from the surroundingatmosphere and from the bracket means 1 1A, a cylindrical metallicsleeve 39 is provided and has a first portion 40 fully receiving thebulb portion 31 therein and a second portion 41 extending from the end42 of the bulb portion 31 to the left in FIG. 2 a sufficient distance tocarry the same well beyond the juncture area 33 whereby a substantiallydead airspace 43 is provided in the sleeve 39 to completely surround thejuncture area 33 as well as a portion of the tube means 34 leading fromthe juncture area 33 so as to prevent a high temperature gradientbetween the bulb portion 31 and the juncture area 33 when the burnermeans 12A is creating the flame means 14A.

The sleeve 39 has opposed open ends 44 and 45, the open end 45 extendingbeyond the free end 32 of the bulb portion 31 and being suitably neckedinwardly at 46 adjacent the end 32 of the bulb 31 and necked inwardly bya plurality of dimples 47 adjacent the other end 42 of the bulb portion31 so as to maintain the sleeve 39 in assembled relation on the bulbportion 31 in the configuration illustrated in FIG. 2.

Thus, it can be seen that the necked portion 45 of the sleeve 39 can bereceived in the opening means 18A of the flame shield A to support theforward end thereof and the second portion 41 of the sleeve 39 can bereceived in the opening means 24A of the bracket means 11 to support theother end thereof whereby the sleeve 39 can be utilized in conventionalbracket means to provide the unique function previously described.

The above inward necking 47 and 46 of the sleeve 39 is accomplished in amanner to prevent the deforming of the bulb portion 31 while stilllimiting play between the sleeve 39 and the bulb portion 31 to atolerable degree.

While the sleeve 39 could be formed of any suitable material to providethe aforementioned function, it has been found that when the bulb 31 andcapillary tube 34 are formed from metallic tubing material AFT M-446having an original diameter of the desired bulb size 31 so that the samecan be subsequently swedged down to form the capillary portion in aconventional manner whereby the capillary portion 34 and bulb portion 31are integral at the juncture area 33, the sleeve 39 for such a formedbulb 31 can comprise lncoloy tubing of the International Nickel Companyhaving a composition of approximately to 35 percent nickel; 19 to 23percent chromium; a maximum 0.1 percent carbon; a maximum of 1% percentmanganese; a maximum of 0.03 percent sulphur; a maximum of 1 percentsilicon; and a maximum of 0.75 percent copper with the remainder beingiron.

Such a sleeve 39 has an inside diameter of approximately 0.130 inch anda wall thickness of approximately 0.020 inch. Such a tube isapproximately 1.750 inches in length for a bulb length of approximately0.800 inch.

In view of the above, it can be seen that this invention not onlyprovides an improved condition responsive means for a pilot burner orthe like, but also this invention provides an improved method of makingsuch a condition responsive means or the like.

While the form of the invention now preferred has been disclosed, asrequired by statute, other forms may be used, all coming within thescope of the claimed subject matter which follows. I

What is claimed is:

1. In combination, a burner, a controlled device to be responsive toflames at said burner, bracket means carrying said burner, aflame-sensing bulb portion carried by said bracket means and having anexterior wall means defining chamber means in said bulb portion, saidbulb portion being located by said bracket means in the flame area ofsaid burner, tube means interconnected to said bulb portion andproviding fluid communication therethrough from said chamber to saidcontrolled device whereby said tube means and said bulb portion define ajuncture area therebetween, said bulb having a relatively largetransverse cross-sectional dimension in relation to the relatively smalltransverse cross-sectional dimension of said tube means at said juncturearea whereby said tube means has a tendency to fail and break off atsaid juncture area when a relatively wide temperature gradient isrepetitively created between said bulb portion and said tube means atsaid juncture area, and means insulating said juncture area at theexterior thereof from the atmosphere and from said bracket means so thatsubstantially no adverse wide temperature gradient is created betweensaid bulb portion and said juncture'area when said bulb portion issubjected to relatively high temperatures provided by said flame meansissuing from said burner and surrounding said bulb portion.

- 2. A combination as set forth in claim 1 wherein said lastnamed meansalso insulates said tube means from said juncture area to a poir itspaced from said bulb portion.

3. A combination as set forth in claim 1 wherein said lastnamed meansinsulates said juncture area by providing a substantially dead airspaceabout the same.

4. A combination as set forth in claim 1 wherein said lastnamed meanscomprises a sleeve disposed about said juncture area to provide asubstantially dead airspace about the same.

5. A combination as set forth in claim 4 wherein said sleeve has a firstportion receiving said bulb portion therein and a second portionextending from said bulb portion in telescoping spaced relation aboutsaid tube means, said sleeve being carried by said bracket means wherebysaid bulb portion is carried by said bracket means.

6. A combination as set forth in claim 5 wherein said sleeve 7 hasopposed open ends respectively at said first and second ture area andthe open end at said second portion extending along said tube means awayfrom said juncture area in the opposite direction.

7. A combination as set forth in claim 6 wherein said bulb portion hasopposed ends and wherein said first portion of said sleeve is neckedinwardly adjacent said bulb portion at said opposed ends thereof to holdsaid sleeve on said bulb portion.

8. A combination as set forth in claim 7 wherein one of said ends ofsaid bulb portion is a closed end and the other end of said bulb portionis necked inwardly to said tube means and defines said juncture areatherewith.

1. In combination, a burner, a controlled device to be responsive toflames at said burner, bracket means carrying said burner, aflame-sensing bulb portion carried by said bracket means and having anexterior wall means defining chamber means in said bulb portion, saidbulb portion being located by said bracket means in the flame area ofsaid burner, tube means interconnected to said bulb portion andproviding fluid communication therethrough from said chamber to saidcontrolled device whereby said tube means and said bulb portion define ajuncture area therebetween, said bulb having a relatively largetransverse cross-sectional dimension in relation to the relatively smalltransverse cross-sectional dimension of said tube means at said juncturearea whereby said tube means has a tendency to fail and break off atsaid juncture area when a relatively wide temperature gradient isrepetitively created between said bulb portion and said tube means atsaid juncture area, and means insulating said juncture area at theexterior thereof from the atmosphere and from said bracket means so thatsubstantially no adverse wide temperature gradient is created betweensaid bulb portion and said juncture area when said bulb portion issubjected to relatively high temperatures provided by said flame meansissuing from said burner and surrounding said bulb portion.
 2. Acombination as set forth in claim 1 wherein said last-named means alsoinsulates said tube means from said juncture area to a point spaced fromsaid bulb portion.
 3. A combination as set forth in claim 1 wherein saidlast-named means insulates said juncture area by providing asubstantially dead airspace about the same.
 4. A combination as setforth in claim 1 wherein said last-named means comprises a sleevedisposed about said juncture area to provide a substantially deadairspace about the same.
 5. A combination as set forth in claim 4wherein said sleeve has a first portion receiving said bulb portiontherein and a second portion extending from said bulb portion intelescoping spaced relation about said tube means, said sleeve beingcarried by said bracket means whereby said bulb portion is carried bysaid bracket means.
 6. A combination as set forth in claim 5 whereinsaid sleeve has opposed open ends respectively at said first and secondportions thereof, the open end at said first portion extending beyondsaid bulb portion in a direction away from said juncture area and theopen end at said second portion extending along said tube means awayfrom said juncture area in the opposite direction.
 7. A combination asset forth in claim 6 wherein said bulb portion has opposed ends andwherein said first portion of said sleeve is necked inwardly adjacentsaid bulb portion at said opposed ends thereof to hold said sleeve onsaid bulb portion.
 8. A combination as set forth in claim 7 wherein oneof said ends of said bulb portion is a closed end and the other end ofsaid bulb portion is necked inwardly to said tube means and defines saidjuncture area therewith.